Improved Synthesis of 1-Bromo-3-buten-2-one |
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| Authors: | Rolf Carlson Alexandre Descomps Alemayehu Mekonnen Andreas Westerlund Martina Havelkova |
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| Affiliation: | 1. Department of Chemistry , University of Tromsoe , Tromsoe , Norway rolf.carlson@chem.uit.no;3. Department of Chemistry , University of Tromsoe , Tromsoe , Norway;4. Cambrex Karlskoga AB , Karlskoga , Sweden;5. Institute of Pharmacy, University of Tromsoe , Tromsoe , Norway |
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| Abstract: | A convenient procedure for the synthesis of 1-bromo-3-buten-2-one, 4, from commercially available 2-ethyl-2-methyl-1,3-dioxolane, 1, is described. The procedure involves three reaction steps: (1) The acetal 1 is converted to 2-(1-bromoethyl)-2-bromomethyl-1,3-dioxolane, 2, by reacting 1 with elemental bromine in dichloromethane to yield 98% of 2. (2) Dehydrobromination of 2 with potassium tert-butoxide in tetrahydrofuran gives 2-bromomethyl-2-vinyl-1,3-dioxolane, 3, in 84–93% yield. (3) Removal of the acetal protection from 3 by formolysis for 6–10 h afforded 1-bromo-3-buten-2-one, 4, in 85–94% yield. A more rapid method is acid hydrolysis of 3 under microwave activation (100 °C, 8–10 min), by which 4 was obtained in 75% yield. Full experimental details are given.  Additional information ACKNOWLEDGMENTS We thank the American Chemical Society for the kind permission to reproduce the experimental proceddure for the synthesis of the dibromoactal, 2 published in Ref. [2]. We also thank the Research Council of Norway for financial support via the KOSK-II program. |
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| Keywords: | Acetal deprotection bromination 2-bromomethyl-2-vinyl-1,3-dioxolane dehydrobromination formolysis microwave activation |
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